Page 1 of 3 123 LastLast
Results 1 to 15 of 31

Thread: I just don't get negative rake scrapers.

  1. #1
    Join Date
    Jun 2011
    Location
    Colby, Washington. Just across the Puget Sound from Seattle, near Blake Island.
    Posts
    817

    I just don't get negative rake scrapers.

    It seems like everyone is climbing onto the negative rake scraper bandwagon but, frankly, I just don't get it. I use scrapers all the time and get really good results with nary a catch. Perhaps that's because I grind mine at 85 degrees. I mean, by adding a "negative rake" to your scraping edge you're essentially making the grind angle steeper.

    When I want to make the edge a bit steeper (effectively exposing more of the burr to the wood) all I need to do is raise my tool rest.

    Somebody throw out a nugget of wisdom to convince me otherwise.
    Russell Neyman.

    Writer - Woodworker - Historian
    Past President, Olympic Peninsula Woodturners
    West Puget Sound, Washington State


    "Outside of a dog, there's nothing better than a good book; inside of a dog it's too dark to read."

  2. For me, the negative rake scraper is such a finesse tool, because it really takes the tiniest of shavings, and will allow for good clean up of difficult grain. The drawback is that the edge must be refreshed every 15-20 seconds depending on the wood you are trying to cut.

    I saw Rudy Lopez use the NRS at our Virginia symposium, and while I had been using it all along, his instruction opened my eyes to how good they really are at finessing the grain so that sanding can a lot of times be started at 220-320 grit.

    That was worth me purchasing a Thompson 1.25" scraper and making myself a totally new negative rake tool.
    Remember, in a moments time, everything can change!

    Vision - not just seeing what is, but seeing what can be!




  3. #3
    Last edited by Brian Deakin; 06-07-2019 at 6:49 PM.

  4. #4
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    8,120
    Quote Originally Posted by Russell Neyman View Post
    It seems like everyone is climbing onto the negative rake scraper bandwagon but, frankly, I just don't get it. I use scrapers all the time and get really good results with nary a catch. Perhaps that's because I grind mine at 85 degrees. I mean, by adding a "negative rake" to your scraping edge you're essentially making the grind angle steeper.

    When I want to make the edge a bit steeper (effectively exposing more of the burr to the wood) all I need to do is raise my tool rest.

    Somebody throw out a nugget of wisdom to convince me otherwise.
    I converted most of my scrapers to NRS after some experimenting. I find the NRS far easier to hold for finer and easier control than the conventional, flat-topped scrapers. The top bevel lets the scraper be held horizontal on the tool rest instead of angling the tool downwards.

    Also, a NRS is easier to use inside a hollowed piece or bowl since the top bevel automatically "tilts" the edge while the tool remains horizontal.

    Note that my scraper use is very gentle, to remove tool marks in dry wood. Those who remove wood or hollow aggressively with scrapers will work differently. As many things in turning, the tools and methods one person uses often depends on on the type of turning, the type of wood, and their level of experience.

    If it wasn't such a long walk, I'd say stop by and I'll let you try a variety of grinds for yourself.

    JKJ

  5. #5
    This is a video topic I need to cover, and I am almost there.... So, there are two types, one is more like a skew chisel, same bevel on both sides, in the 25/25 to 30/30 range, though that varies. The other style is closer to the standard scrapers with a 60 or 70 degree bevel on the down side, and a 20 to 30 degree bevel on the bottom side. Both styles cut with burrs. There are 3 ways to make the burr. One is straight off the grinder, standard grind, where you touch up the top side, and then regrind the bottom bevel with the scraper right side up. The other straight off the grinder burr is done by sharpening the bottom bevel with the scraper up side down on the grinder platform. Those who sharpen upside down claim it is a sharper burr. (It can be done on my robo rest if you tip the platform forward and slip the pin through the 90 degree hole so the pin rests against the yoke rather than going through the sleeves for about a -70 degree angle, thanks Kathleen Duncan for that tip). I have to play with this a lot more to see if I notice any big differences. First experiments seem to make me think that the upside down burr is weaker than the right side up burr, but not positive. The third method is to burnish a burr. With the skew chisel type NRSs, this does not work well because of the acute angle, you can actually hear the metal edge breaking as you burnish, no matter how gentle you are. The more blunt angled NRSs can burnish a very fine and very durable burr. The burr from the grinders are very fragile, and gone in seconds, making it a high maintenance tool. If you have to push at all, it is dull. The burnished burr is much stronger and, to me, it cuts better.

    Now, for using them. On bowls, especially, much of it depends on the wood. Generally harder woods will result in a finer surface than softer woods. I do find them useful for sweeping across the bottoms of bowls, and barely into the transition area. I don't like them for going up the sides of bowls. They are still scrapers, and will pull on the fibers when you are cutting up hill, and generally I will get a cleaner surface with a burnished burr shear scrape rather than a NRS scrape. Again, that can depend on the wood. These are not tools to be used for any stock removal. At best you can smooth out ripples, but nothing more. I have used the burnished burr NRS for shear scraping some times as well Still experimenting, but I tend to want to hone off the grinder burr first because I get a better raised burr most of the time. Some times when I am feeling lazy, I use the grinder burr till it is dull, then burnish it down, then back up. The burnished burr can be turned down and bought back up a few times before you need to go back to the grinder. I do think the burnished burr on a standard 70 degree bevel scraper works better than the burnished burr on a NRS. No idea why, but more experimenting needed. Again, some times hard to tell because the particular wood can make a lot of difference.

    I do love them for end grain, especially for boxes. You can leave glass smooth surfaces on most end grain, and with some practice, you can end up with surfaces that need no sanding. This is where I think the NRS excels beyond any other tool I have used.

    I have been turning a lot of Bay Laurel (we call it Myrtle wood...) and the two logs I have are very different, and so are different parts of each log.

    robo hippy

  6. #6
    Join Date
    Jun 2011
    Location
    Colby, Washington. Just across the Puget Sound from Seattle, near Blake Island.
    Posts
    817
    Quote Originally Posted by Reed Gray View Post
    So, there are two types, one is more like a skew chisel, same bevel on both sides, in the 25/25 to 30/30 range, though that varies. The other style is closer to the standard scrapers with a 60 or 70 degree bevel on the down side, and a 20 to 30 degree bevel on the bottom side. Both styles cut with burrs. There are 3 ways to make the burr....

    On bowls, especially, much of it depends on the wood. Generally harder woods will result in a finer surface than softer woods. I do find them useful for sweeping across the bottoms of bowls, and barely into the transition area.... I will get a cleaner surface with a burnished burr shear scrape rather than a NRS scrape.... At best you can smooth out ripples, but nothing more. I have used the burnished burr NRS for shear scraping some times as well....Again, some times hard to tell because the particular wood can make a lot of difference.,,,

    robo hippy
    At the heart of this is a topic that is largely a mystery to most woodturners: raising a burr. Truth is, you can create a burr (a small,sharp ridge on the topside of a sharpened edge) on any tool and put it to use, including bowl gouges. If anyone wants to understand this concept, watch a few videos on card scrapers, which I employ fairly often on the insides of bowls.

    The point is, negative rake scrapers are hardly a replacement to "regular" scrapers and, while they can do a few things, really aren't helpful in removing large quantities of the inside of a vessel, which is what most of us use them for.
    Russell Neyman.

    Writer - Woodworker - Historian
    Past President, Olympic Peninsula Woodturners
    West Puget Sound, Washington State


    "Outside of a dog, there's nothing better than a good book; inside of a dog it's too dark to read."

  7. #7
    Quote Originally Posted by Russell Neyman View Post
    The point is, negative rake scrapers are hardly a replacement to "regular" scrapers and, while they can do a few things, really aren't helpful in removing large quantities of the inside of a vessel, which is what most of us use them for.
    Russell, I think this is an accurate statement except for the last clause. You may have been referring to scrapers collectively in your statement, but I doubt most of us use NRS to remove large quantities of wood. Actually, of those that use them and use them correctly, I would think just the opposite - that they are finishing tools only on face grain, though on end grain application they can remove more material cleanly. But, still, I think they should be viewed as a finishing tool to diminish sanding. But, I haven't surveyed the masses and perhaps my use of them is in the minority.

    Left click my name for homepage link.

  8. #8
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    8,120
    Quote Originally Posted by Russell Neyman View Post
    The point is, negative rake scrapers are hardly a replacement to "regular" scrapers and, while they can do a few things, really aren't helpful in removing large quantities of the inside of a vessel, which is what most of us use them for.
    This is true, they are not useful replacements for hogging tools. They are finishing tools. I use the NRS just after my finish gouge cuts and just before the hand scrapers or hand sanding, on bowls, platters, vessels, whatever, inside and out. Once you learn how effective they are it would be difficult to go back to other methods.

    I also use negative rake scrapers for glass-smooth surfaces on end grain in good, hard, wood, such as on the bottoms and lids of lidded boxes. I've made a variety of shapes and sizes from 1/8" up.

    Raising a burr on scrapers has been discussed here. I personally prefer burnishing a burr rather than rely on the ragged burr from a grinder which I remove by honing, just like preparing card scrapers.

    JKJ

  9. #9
    Join Date
    Jun 2011
    Location
    Colby, Washington. Just across the Puget Sound from Seattle, near Blake Island.
    Posts
    817
    That's exactly my point. I use scrapers to hog out a ton of wood quickly, but the NRS is not useful for that.
    Russell Neyman.

    Writer - Woodworker - Historian
    Past President, Olympic Peninsula Woodturners
    West Puget Sound, Washington State


    "Outside of a dog, there's nothing better than a good book; inside of a dog it's too dark to read."

  10. I use a bowl gouge to hog out wood quickly, and in my opinion, the gouge is a much more proficient cutting tool. Plus, scrapers tear the grain, and a gouge cuts the grain, which cuts down considerably on sanding etc, with the right tool presentation........to each his own.
    Remember, in a moments time, everything can change!

    Vision - not just seeing what is, but seeing what can be!




  11. #11
    Join Date
    Aug 2007
    Location
    Lakewood, CO
    Posts
    652
    NRS are finesse tools, they are not aggressive and will not self feed. It's nearly if not impossible to get a catch. You can shove the edge right into the wood and not get a catch (something you would never do with a conventional scraper). For these reasons a NRS is also a good choice for newbies or less experienced turners since the learning curve is practically nonexistent. Pick one up and a minute later you are getting good results. As others have said they are used flat on the tool rest. You don't have to worry about angling the edge or what angle the tool edge is at. Think shear scraping with the tool held flat might best describe a NRS.

  12. #12
    Standard scrapers have their place, and for me as a production turner, they are the most efficient tool for removing lots of bulk, especially from bowl blanks. On bowls, they don't leave a nice surface down the sides of the bowl, which is why it is called 'roughing'. They do a good job for sweeping across the bottom. I have heard the NRS compared to the shear scrape. These are two entirely different cuts. The only similarity between the two is that neither one seems to be able to generate a catch. The NRS is a scraping cut, with the cutting edge at 90 degrees to the rotation, and like the standard scraper, they do a better job of sweeping across the bottom, and not nearly as good of a job of going through the transition and up the sides of a bowl. The 'shear scrape' is not a scraping cut at all. It is called that because the tool is not guided by a bevel rub. The high shear angle does a much better job of gently lifting the fibers as they cut rather than pulling like scrapers do. How clean the resulting surface is depends on the wood, how sharp the tool is, and 'presentation' of the cutting edge to the wood. Most of the time, on bowl sides, I can get a cleaner surface with the shear scrape than I can with the NRS.

    robo hippy

  13. #13
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    8,120
    Quote Originally Posted by Reed Gray View Post
    ...I have heard the NRS compared to the shear scrape. These are two entirely different cuts. The only similarity between the two is that neither one seems to be able to generate a catch. The NRS is a scraping cut, with the cutting edge at 90 degrees to the rotation, and like the standard scraper, they do a better job of sweeping across the bottom, and not nearly as good of a job of going through the transition and up the sides of a bowl. The 'shear scrape' is not a scraping cut at all. It is called that because the tool is not guided by a bevel rub. The high shear angle does a much better job of gently lifting the fibers as they cut rather than pulling like scrapers do. How clean the resulting surface is depends on the wood, how sharp the tool is, and 'presentation' of the cutting edge to the wood. Most of the time, on bowl sides, I can get a cleaner surface with the shear scrape than I can with the NRS.

    robo hippy
    I use this shape for the bottom, transition, and inside and outside of bowls. The flat at the end is perfect for wings, shallow dishing, and bottoms. For me, the shape is useful in more places than shear scraping with the wings of a gouge. I grind mine to 60-deg included angle, symmetrically so I can flip one over as needed, adding the appropriate burr of course.

    _scrapers_IMG_7778.jpg scrapers_neg_rake.jpg

    These are Thompson steel, ground from his scrapers and a skew chisel. The surface is excellent in good wood, sometimes needing only a little sanding by hand.

    JKJ

  14. #14
    Russell,

    The negative rake scraper is essential a regular scraper with a pre-installed downward pitch, also know as raising the handle.

    Happy Turning,
    Kent
    Last edited by Steve Schlumpf; 06-23-2019 at 7:02 PM. Reason: Deleted link was in violation of TOS

  15. #15
    Russel this is my feeling exactly BUT with so many world class turners now using NRS I wonder if we are missing the boat. I for one can hardly wait for Reed's Video1
    Quote Originally Posted by Kent Weakley View Post
    Russell,

    The negative rake scraper is essential a regular scraper with a pre-installed downward pitch, also know as raising the handle.

    Happy Turning,
    Kent
    Pete


    * It's better to be a lion for a day than a sheep for life - Sister Elizabeth Kenny *
    I think this equates nicely to wood turning as well . . . . .

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •